The present invention relates to the suppression of "glitches", i.e., those unwanted variations in control signals which result from contact bounce, interference of various types and/or noise.
Low voltage control signals are applied to semiconductor devices for myriad reasons, and an unwanted variation in such control signals often has serious adverse effects on the operation of the circuit. It is known to suppress these temporary variations by requiring that any change in the control signal appear for a predetermined finite period of time before it is recognized as a desired control signal and not as an undesired transient. By way of example, U.S. Pat. No. 4,525,635 dated Jun. 25, 1985 discloses the use of two bistable devices as a transient suppression circuit, with the two bistable devices used to sample the control signal at two different times and concurrence of the bistable devices required for propagation of the control signal into the circuit. In this way, the binary state of the control signal must remain constant over the two samples for the signal to be recognized as a control signal, and the glitch suppression circuit acts as a filter for transients having less duration than the two samples.
However, there are times when it is desired to bypass the glitch suppression circuit and to propagate the control signal directly into the circuit and it is accordingly an object of the present invention to provide a novel circuit and method for selectively bypassing a glitch suppression circuit.
It is another object of the present invention to provide a novel selectively bypassable glitch suppression circuit which can be integrated into the control lines for an operating circuit.
It is a further object of the present invention to provide a novel selectively operable transient filter circuit and method.
It is yet another object of the present invention to provide a novel circuit and method which may be integrated into the design of a semiconductor device without regard to the desirability of the glitch suppression circuit in the application of the integrated circuit.
It is still another object of the present invention to provide a novel integrated circuit and method which contains a glitch suppression circuit in every input line and thus avoids any additional constraint from either temperature or process parameters on the operating circuit.
These and many other objects and advantages will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of a preferred embodiment.